U.S. patent number 6,042,656 [Application Number 08/953,133] was granted by the patent office on 2000-03-28 for shutoff control methods for surface treating machines.
This patent grant is currently assigned to Nilfisk-Advance, Inc.. Invention is credited to Kipp W. Knutson.
United States Patent |
6,042,656 |
Knutson |
March 28, 2000 |
Shutoff control methods for surface treating machines
Abstract
An apparatus (200) is provided in a floor scrubber (10) for
automatically shutting off the motor (60) which rotates an agitator
(64) and the motor (96) of a vacuum assembly under various
operating conditions of the floor scrubber (10). The current to the
motors (60, 96) is detected by devices (204, 206) and monitored by
a control circuit (202) controlling devices (208, 210 which
interrupt operation of the motors (60, 96). In the preferred form,
operation of the agitator (64) is interrupted when the current to
the brush motor (60) is less than or equal to a threshold level
indicating that the agitator (64) has been raised from the floor
surface as the current to the brush motor (60) would be above the
threshold level when the agitator (64) engages the floor surface.
Operation of the vacuum assembly is interrupted when the current to
the vacuum motor (96) drops to a fixed percentage over a period of
time from normal operating levels indicating the path of the air in
the vacuum assembly has been blocked.
Inventors: |
Knutson; Kipp W. (Shorewood,
MN) |
Assignee: |
Nilfisk-Advance, Inc.
(Plymouth, MN)
|
Family
ID: |
25493618 |
Appl.
No.: |
08/953,133 |
Filed: |
October 17, 1997 |
Current U.S.
Class: |
134/21; 134/6;
15/319; 15/320; 15/50.1 |
Current CPC
Class: |
A47L
7/0009 (20130101); A47L 7/0028 (20130101); A47L
9/2831 (20130101); A47L 9/2842 (20130101); A47L
11/30 (20130101); A47L 11/4005 (20130101); A47L
11/4011 (20130101); A47L 11/4069 (20130101); A47L
11/4077 (20130101) |
Current International
Class: |
A47L
11/00 (20060101); A47L 11/30 (20060101); A47L
11/40 (20060101); A47L 11/29 (20060101); A47L
9/28 (20060101); A47L 7/00 (20060101); A47L
005/00 () |
Field of
Search: |
;15/49.1,50.1,319,320,340.1,340.3,340.2,389,390 ;96/158,165,406
;134/6,21 ;118/207 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
5-146386 |
|
Jun 1993 |
|
JP |
|
6-105770 |
|
Apr 1994 |
|
JP |
|
Other References
M2700-ABA Automatic Burnishing System, Minuteman International,
Illinois, Oct. 1997, 986740-20N (No Date)..
|
Primary Examiner: Till; Terrence R.
Attorney, Agent or Firm: Kamrath; Alan Oppenheimer, Wolff
& Donnelly, LLP
Claims
What is claimed is:
1. A vacuum assembly comprising, in combination: a recovery vessel;
an air moving device in fluid communication with the recovery
vessel for removing air from the recovery vessel; a vacuum motor
coupled to the air moving device; an inlet to the recovery vessel
allowing the entry of air into the recovery vessel, with the air
flowing in a path through the inlet, the recovery vessel, and the
air moving device; and means for detecting a blockage in the path
of the air and interrupting operation of the vacuum motor; wherein
the detecting means monitors the current level to the vacuum motor
and interrupts the current to the vacuum motor when the current
level drops to a fixed percentage over a fixed period of time.
2. The vacuum assembly of claim 1 wherein the detecting means
interrupts operation of the vacuum motor after a time delay so that
the vacuum motor will not be inadvertently shut off if the path of
the air is momentarily restricted.
3. A vacuum assembly comprising, in combination: a recovery vessel;
an air moving device in fluid communication with the recovery
vessel for removing air from the recovery vessel; a vacuum motor
coupled to the air moving device; an inlet to the recovery vessel
allowing the entry of air into the recovery vessel, with the air
flowing in a path through the inlet, the recovery vessel, and the
air moving device; and means for detecting a blockage in the path
of the air and interrupting operation of the vacuum motor; wherein
the detecting means interrupts operation of the vacuum motor after
a time delay so that the vacuum motor will not be inadvertently
shut off if the path of the air is momentarily restricted.
4. The vacuum assembly of claim 3 wherein the recovery vessel is a
tank for holding solutions; and wherein the vacuum assembly further
comprises, in combination: a mechanical float for blocking fluid
communication between the recovery vessel and the air moving
device.
5. The vacuum assembly of claim 4 wherein the inlet includes a
squeegee assembly for wiping a surface to be treated and a hose
extending and in fluid communication between the inlet of the
recovery tank and the squeegee assembly.
6. The vacuum assembly of claim 3 wherein the detecting means
monitors the current level to the vacuum motor and interrupts the
current to the vacuum motor when the current level drops to a fixed
percentage over a fixed period of time.
7. A surface treating machine comprising, in combination: an
agitator for contacting the surface to be treated; a brush motor
coupled to the agitator for rotating the agitator; means for moving
the agitator between a raised position and a lowered position, with
the agitator being elevated from the surface in the raised position
and engaging the surface in the lowered position; and means for
detecting that the agitator is in the raised position and
interrupting operation of the brush motor after an opportunity to
move the agitator to the lowered position.
8. The surface treating machine of claim 7 wherein the detecting
means interrupts operation of the brush motor only after the brush
motor has rotated the agitator in the lowered position.
9. The surface treating machine of claim 7 wherein the brush motor
exhibits a first operating condition when the agitator is in the
lowered position and is being rotated by the brush motor while
engaged with the surface and exhibits a second operating condition
when the agitator is in the raised position and is rotated by the
brush motor while elevated from the surface, with the detecting
means detecting the second operating condition.
10. The surface treating machine of claim 9 wherein the current to
the brush motor in the first operating condition is above a
threshold level; and wherein the detecting means detects when the
current to the brush motor is equal to or less than the threshold
level.
11. A vacuum method comprising the steps of: providing a recovery
vessel having an inlet allowing the entry of air into the recovery
vessel; removing air from the recovery vessel by an air moving
device in fluid communication with the recovery vessel and coupled
to a vacuum motor, with the air flowing in a path through the
inlet, the recovery vessel, and the air moving device; and
detecting a blockage in the path of the air and interrupting
operation of the air moving device comprising the step of
monitoring the current level to the vacuum motor and interrupting
the current to the vacuum motor when the current level drops to a
fixed percentage over a fixed period of time.
12. The vacuum method of claim 11 wherein the detecting step
comprises the step of interrupting operation of the air moving
device after a time delay so that the air moving device will not be
inadvertently shut off if the path of the air is momentarily
restricted.
13. A vacuum method comprising the steps of: providing a recovery
vessel having an inlet allowing the entry of air into the recovery
vessel; removing air from the recovery vessel by an air moving
device in fluid communication with the recovery vessel, with the
air flowing in a path through the inlet, the recovery vessel, and
the air moving device; and detecting a blockage in the path of the
air and interrupting operation of the air moving device after a
time delay so that the air moving device will not be inadvertently
shut off if the path of the air is momentarily restricted.
14. The vacuum method of claim 13 wherein the recovery vessel
providing step comprises the step of providing a tank for holding
solutions; and wherein the vacuum method further comprises the step
of: providing a mechanical float for blocking fluid communication
between the recovery vessel and the air moving device.
15. The vacuum method of claim 14 further comprising the steps of:
providing a squeegee assembly for wiping a surface to be treated;
and providing a hose extending and in fluid communication between
the inlet of the recovery tank and the squeegee assembly.
16. The vacuum method of claim 13 wherein the air removing step
comprises the step of removing air by the air moving device coupled
to a vacuum motor; and wherein the detecting step comprises the
step of monitoring the current level to the vacuum motor and
interrupting the current to the vacuum motor when the current level
drops to a fixed percentage over a fixed period of time.
17. A method for treating a surface comprising the steps of:
providing an agitator for contacting the surface to be treated;
providing a brush motor coupled to the agitator for rotating the
agitator; moving the agitator between a raised position and a
lowered position, with the agitator being elevated from the surface
in the raised position and engaging the surface in the lowered
position; and detecting that the agitator is in the raised position
and interrupting operation of the brush motor after an opportunity
to move the agitator to the lowered position.
18. The surface treating method of claim 17 wherein the detecting
step comprises the step of interrupting operation of the brush
motor only after the brush motor has rotated the agitator in the
lowered position.
19. The surface treating method of claim 17 wherein the brush motor
providing step comprises the step of providing the brush motor
exhibiting a first operating condition when the agitator is in the
lowered position and is being rotated by the brush motor while
engaged with the surface and exhibiting a second operating
condition when the agitator is in the raised position and is
rotated by the brush motor while elevated from the surface, with
the detecting step comprising the step of detecting the second
operating condition.
20. The surface treating method of claim 19 wherein the detecting
step comprises the step of detecting when the current to the brush
motor is equal to or less than a threshold level, with the current
to the brush motor in the first operating condition being above the
threshold level.
21. A surface treating machine comprising, in combination: an
agitator for contacting the surface to be treated; a brush motor
coupled to the agitator for rotating the agitator; means for moving
the agitator between a raised position and a lowered position, with
the agitator being elevated from the surface in the raised position
and engaging the surface in the lowered position; means for
detecting that the agitator is in the raised position and
interrupting operation of the brush motor after an opportunity to
move the agitator to the lowered position; and a vacuum assembly
comprising, in combination: a recovery vessel; an air moving device
in fluid communication with the recovery vessel for removing air
from the recovery vessel; a vacuum motor coupled to the air moving
device; an inlet to the recovery vessel allowing the entry of air
into the recovery vessel, with the air flowing in a path through
the inlet, the recovery vessel, and the air moving device; and
means for detecting a blockage in the path of the air and
interrupting operation of the vacuum motor.
Description
BACKGROUND
The present invention relates generally to motor control methods
and particularly to automatic methods for shutting off motors under
various operating conditions encountered in the operation of floor
cleaning machines.
A floor cleaning machine for cleaning large floor areas as in
hotels, offices and the like will typically include two motors. A
first motor 60, sometimes referred to as a brush motor, is coupled
to a rotating agitator 64 which contacts the surface to be treated
or cleaned. A second motor 96, sometimes referred to as a vacuum
motor, is coupled to an air moving device 94 for creating
directional air flow so as to remove cleaning solutions and/or
debris from the surface being cleaned and placing the picked up
solution and/or debris into a recovery vessel such as a tank
90.
One type of floor cleaning machines for which the present invention
has particular application is a floor scrubber 10. In floor
scrubbers, the rotating agitator 64 can be in the form of a brush.
However, due to the particular floor surface to be cleaned or the
particular cleaning operation desired to be performed, the rotating
agitator 64 often is in the form of a pad 164 held on a pad holder
166 by a retainer 168. To maximize pad life and for maximum
cleaning ability, it is desirable to invert the pad 164 on the pad
holder 166 on occasion. Floor scrubbers 10 include some provisions
for moving the agitator 64 between a raised and lowered position.
In the lowered position, the agitator 64 is in its working position
and engages the floor surface. In the raised position, the rotating
agitator 64 is in a transport position elevated from the floor
surface at least for ease of transport between cleaning surfaces or
between its storage location and the surface desired to be cleaned.
Typically, such provisions are in the form of a lift lever 56 which
is pivoted by the foot of the operator. The brush motor 60 is
controlled by an electric switch on the console of the floor
scrubber 10. When the operator desired to invert the pad 164, the
operator would move the lift lever 56 to raise the rotating
agitator 64 off the floor to obtain access to the retainer 168 of
the pad 164. However, the operator often forgot to turn off the
electric switch controlling the brush motor 60. As the pad 164 and
retainer 168 are positioned on the underside of the floor scrubber
10, visibility may be limited or otherwise restricted. Thus, injury
to the operator may occur if the operator attempts to remove the
retainer 168 and pad 164 without realizing the agitator 64 is still
rotating.
Thus, a need exists to automatically shut off the brush motor 60
when the rotating agitator 64 is raised off the floor surface at
least for safety reasons.
Also, it is clearly desirable to prevent solution from passing from
the recovery tank 90 into the air moving device 94. One prior
attempt to solve this problem was to provide a float operated
mechanical switch in the recovery tank 90. However, at least due to
the exposure of such switches to moisture in the recovery tank,
reliability issues have arisen. Additionally, problems also occur
(especially when the recovery tank 90 is close to being full but
not full enough to turn off the mechanical switch) of the cleaning
solution sloshing through the outlet of the recovery tank and being
drawn into the air moving device 94. Thus, a preferred method of
solving this problem is to provide a mechanical float 170 which
shuts off the outlet of the recovery tank 90 and thus blocks fluid
communication between the recovery tank 90 and the air moving
device 94. The problem is that when the recovery tank 90 is full
and the mechanical float 170 blocks off the outlet of the recovery
tank 90, the vacuum motor 96 continues to drive the air moving
device 94 but the cleaning solution and/or debris are not removed
from the floor surface as air flow is blocked. However, the
operator may not realize this has occurred until cleaning solution
being pushed in front of the squeegee provisions 144 is visible
beyond the sides of scrubber 10 or behind scrubber 10. Although the
sound or pitch of the air moving device 94 may change when the air
flow is blocked, the operator may not notice this change due to
lack of attention or other distractions and can especially be
difficult to ascertain when floor scrubbers 10 are designed and
manufactured to reduce or deaden noise generation.
Thus, a need exists to automatically shut off the vacuum motor 96
when the air flow through the air moving device 94 is blocked such
as when the recovery vessel such as a recovery tank 90 is full of
solution and/or debris.
SUMMARY
The present invention solves these needs and other problems in the
field of surface treating machines by providing, in the preferred
form, methods and apparatus for interrupting operation of the
vacuum motor of a vacuum assembly when the path of the air within
the vacuum assembly is detected as being blocked. In most preferred
forms of the present invention, the vacuum assembly is of the wet
type and the vacuum motor operation is interrupted when the
mechanical float in the recovery tank blocks fluid communication
between the recovery tank and the fan or other air moving
device.
In other aspects of the present invention, the present invention
provides methods and apparatus for interrupting operation of the
brush motor when the agitator is detected as being in a raised
position after the operator has had an opportunity to move the
agitator to its lowered position and in the most preferred form
only after the agitator has in fact been moved to and operated in
its lowered position.
It is thus an object of the present invention to provide novel
methods and apparatus for controlling operation of motors in a
surface treating machine.
It is further an object of the present invention to provide such
novel control methods and apparatus for automatically interrupting
operation of surface treating machine motors in the event the loads
to the motor are reduced from normal operating levels.
It is further an object of the present invention to provide such
novel control methods and apparatus for automatically shutting off
the brush motor when the agitator driven thereby is detected as
being raised off the surface.
It is further an object of the present invention to provide such
novel control methods and apparatus for automatically shutting off
the vacuum motor when the recovery vessel is full of solution
and/or debris.
It is further an object of the present invention to provide such
novel control methods and apparatus for automatically shutting off
the vacuum motor when the air flow path through the vacuum assembly
is detected as being blocked other than momentarily.
It is further an object of the present invention to provide such
novel control methods and apparatus providing added operational
convenience for the operator.
It is further an object of the present invention to provide such
novel control methods and apparatus reducing the risk of accidental
injury to the operator when servicing the agitator.
It is further an object of the present invention to provide such
novel control methods and apparatus maximizing run time of a
battery operated surface treating machine.
It is further an object of the present invention to provide such
novel control methods and apparatus reducing wide spread splashing
of solution by the agitator when raised from the surface being
cleaned.
These and further objects and advantages of the present invention
will become clearer in light of the following detailed description
of an illustrative embodiment of this invention described in
connection with the drawings.
DESCRIPTION OF THE DRAWINGS
The illustrative embodiment may best be described by reference to
the accompanying drawings where:
FIG. 1 shows a diagrammatic view of a floor surface treating
machine in the form of a floor scrubber including an apparatus for
controlling operation of motors of the floor scrubber according to
preferred methods of the present invention.
FIGS. 2-5 show graphs illustrating different operating conditions
monitored over time with the apparatus of FIG. 1.
All figures are drawn for ease of explanation of the basic
teachings of the present invention only; the extensions of the
figures with respect to number, position, relationship, and
dimensions of the parts to form the preferred embodiment will be
explained or will be within the skill of the art after the
following description has been read and understood. Further, the
exact dimensions and dimensional proportions to conform to specific
force, weight, strength, and similar requirements will likewise be
within the skill of the art after the following description has
been read and understood.
Where used in the various figures of the drawings, the same
numerals designate the same or similar parts. Furthermore, when the
terms "first", "second", "horizontal", "vertical", and similar
terms are used herein, it should be understood that these terms
have reference only to the structure shown in the drawings as it
would appear to a person viewing the drawings and are utilized only
to facilitate describing the illustrative embodiment.
Description
An apparatus for automatically stopping operation of vacuum motor
96 in a vacuum assembly and of brush motor 60 under various
operating conditions of a floor surface treating machine according
to the preferred methods of the present invention is generally
shown in the drawings and generally designated 200. For purposes of
explanation, the most preferred form of apparatus 200 will be set
forth in connection with floor scrubber 10 of the type set forth in
the BACKGROUND which is hereby incorporated herein by reference.
Additionally, in the most preferred form, floor scrubber 10 is in
the form shown and described in U.S. patent application Ser. No.
08/731,658. For purpose of explanation of the basic teachings of
the present invention, the same numerals designate the same and
similar parts in FIG. 1 hereof and the Figures of U.S. patent
application Ser. No. 08/731,658. The description of the common
numerals and scrubber 10 may be found herein and in U.S. patent
application Ser. No. 08/731,658, which is also hereby incorporated
herein by reference.
Apparatus 200 according to the teachings of the present invention
includes provisions for interrupting operation of brush motor 60
when rotating agitator 64 is detected as being in the raised
position and in the preferred form operation of brush motor 60 is
interrupted only after agitator 64 has been rotatably engaged with
the floor surface and then moved to its raised position. Apparatus
200 includes a control circuit 202 formed by analog, digital, or
microprocessor type circuits and in the most preferred form
includes a microcontroller along with associated discrete devices.
Additionally, apparatus 200 includes first and second devices 204
and 206 for sensing operating conditions of motors 60 and 96,
respectively, with control circuit 202 monitoring the operating
conditions sensed by devices 204 and 206. In the preferred form,
devices 204 and 206 sense the current to motors 60 and 96 and can
be in the form of current coils or fixed resistance devices such as
shunts and in the most preferred form are specific lengths of wire.
Further, apparatus 200 includes first and second devices 208 and
210 for interrupting operation of motors 60 and 96, respectively,
with control circuit 202 controlling the operation of devices 208
and 210. In the preferred form, devices 208 and 210 may be
electronic or electromechanical and in the most preferred form are
in the form of relays.
Now that the basic construction of floor scrubber 10 and apparatus
200 of the most preferred form has been set forth, the operation of
apparatus 200 according to the preferred teachings of the present
invention and some of the advantages obtained thereby will be
explained. Specifically, when power is applied from batteries 68,
70 to control circuit 202, control circuit 202 turns interrupting
devices 208 and 210 off and removes power to brush and vacuum
motors 60 and 96. In the control of brush motor 60, the operator
activates a switch 212 on the console of floor scrubber 10 which
causes control circuit 202 to turn interrupting device 208 on and
thus supplying power from batteries 68, 70 to brush motor 60. After
a short delay to allow the inrush starting current to motor 60 to
subside, control circuit 202 will begin monitoring the current to
motor 60 for a level in excess of a threshold level. This threshold
level will depend upon the particular motor 60 utilized and in the
preferred form is approximately 6 amperes. It can then be
appreciated that motor 60 can be activated with agitator 64 either
in a raised or lowered position. With agitator 64 in the lowered
position and as diagramatically shown in FIG. 2, the current to
motor 60 after the inrush starting current will be at a level
greater than the threshold level and which in the preferred form is
equal to or greater than approximately 7 amperes. With the level of
current to motor 60 being greater than the threshold level,
interrupting device 208 is on and continues to allow power from
batteries 68, 70 to brush motor 60. However, in the event that lift
lever 56 is moved to move agitator 64 from the lowered position to
the raised position so that agitator 64 is spaced from the floor
surface, the current level to motor 60 will drop to the threshold
level. When the current level to motor 60 reaches the threshold
level, sensing device 204 provides an electronic signal to control
circuit 202 which turns interrupting device 208 off and removes
power to brush motor 60 and thereby stops rotation of agitator 64.
Interrupting device 208 remains off until switch 212 is activated
again.
Similarly, with agitator 64 in the raised position when motor 60 is
first activated and as diagrammatically shown in FIG. 3, the
current to motor 60 after the inrush starting current will be at or
below the threshold level and which in the preferred form is
approximately 6 amperes. Although the current may be at the
threshold level, interrupting device 208 remains on and continues
to allow power from batteries 68, 70 to brush motor 60 as the
current level has not exceeded the threshold level aside from the
inrush starting current. The operator moves lift lever 56 to move
agitator 64 from its raised to its lowered position while it is
being rotated by motor 60 so that agitator 64 engages the floor
surface. When agitator 64 engages the floor surface, the current to
motor 60 will exceed the threshold level which in the preferred
form is equal to or greater than approximately 7 amperes. With the
level of current to motor 60 being greater than the threshold
level, interrupting device 208 is on and continues to allow power
from batteries 68, 70 to brush motor 60. However, in the event that
lift lever 56 is moved to move agitator 64 from the lowered
position to the raised position so that agitator 64 is spaced from
the floor surface, the current level to motor 60 will drop to the
threshold level. When the current level to motor 60 reaches the
threshold level, sensing device 204 provides an electronic signal
to control circuit 202 which turns interrupting device 208 off and
removes power to brush motor 60 and thereby stops rotation of
agitator 64. Interrupting device 208 remains off until switch 212
is activated again.
It should be appreciated that the automatic shut off of brush motor
60 when agitator 64 is moved to its raised position according to
the teachings of the present invention is advantageous for several
reasons. First, the risk is greatly reduced of injury to the
operator resulting from the operator not realizing that agitator 64
is rotating when it was desired to service agitator 64.
Specifically, if floor scrubber 10 is being operated to clean a
floor surface and the operator decides to service agitator 64 such
as inverting pad 164, the operator will move lift lever 56 to raise
agitator 64 from its lowered position to its raised position to
allow access to agitator 64. It can then be appreciated that as
soon as agitator 64 is raised, the current to motor 60 drops to the
threshold level so that interrupting device 208 turns off and
interrupts power to motor 60 and stopping rotation of agitator 64.
Thus, the operator forgetting to turn off motor 60 when desired to
service agitator 64 is less likely to occur. Additionally, the
automatic shut off of brush motor 60 when agitator 64 is moved to
its raised position is advantageous for operation convenience for
the operator as a separate operation step is not required to turn
off motor 60 such as moving switch 212 in addition to moving lift
lever 56. Further, the automatic shut off of brush motor 60 when
agitator 64 is moved to its raised position also maximizes run time
of batteries 68, 70 as motor 60 generally does not run in the
raised position. Furthermore, the automatic shut off of brush motor
60 when agitator 64 is moved to its raised position reduces
splashing. Specifically, agitator 64 has a tendency to retain
solution when raised from the floor surface which tends to be
released by agitator 64 and propelled as a result of
circumferential forces outwardly due to the rotation of agitator
64. When agitator 64 is not rotating, the circumferential forces do
not exist and there is less tendency of the solution to be released
from agitator 64. Further, if released from agitator 64 which is
not rotating, the solution will simply drip from the agitator 64
downwardly and is more likely to be retained by the side wipers and
squeegee provisions 144 than if the solution is thrown outwardly
from the rotation of agitator 64.
It should be appreciated that the reason that apparatus 200 of the
present invention does not stop rotation of agitator 64 until after
the current level sensed by device 204 has exceeded the threshold
level is to allow the operator the opportunity to activate motor 60
while agitator 64 is in the raised position and to lower the
agitator 64 to its lowered position after it is rotating. In the
most preferred form, monitoring of the current level to motor 60
does not occur until after agitator 64 has been in fact lowered to
its lowered position and the current level to motor 60 has exceeded
the threshold level (aside from the inrush current associated with
starting motor 60). However, according to the teachings of the
present invention, apparatus 200 could begin to monitor the current
level to motor 60 after a predetermined time has elapsed from the
start of activation of motor 60. This predetermined time would be
sufficient to allow at least an average operator an opportunity to
move lift lever 56 from its raised position to its lowered position
after activation of switch 212. Thus, if the operator forgets to
lower agitator 64 after motor 60 has been activated, apparatus 200
will automatically turn off motor 60 after the passage of the
predetermined time.
In the control of vacuum motor 96, the operator activates a switch
214 on the console of floor scrubber 10 which causes control
circuit 202 to turn interrupting device 210 on and thus supplying
power from batteries 68, 70 to vacuum motor 96. After a short delay
to allow the inrush starting current to motor 96 to subside,
control circuit 202 will begin monitoring the current to motor 96.
It should then be noted that an air flow path exists from the inlet
of squeegee assembly 152 for wiping the floor surface and through
hose 154 and into the inlet of recovery tank 90. From recovery tank
90 and assuming that the level of solution in recovery tank 90 is
such that mechanical float 170 does not block the outlet of
recovery tank 90 and the inlet to air moving device 94, the air
flow path exists from the interior of recovery tank 90 and through
air moving device 94 and the outlet thereof. With the path being
unobstructed, motor 96 will rotate air moving device 94 for
removing air from recovery tank 90 and causing air to be drawn
through the inlet of recovery tank 90, hose 154, and the inlet of
squeegee assembly 152. Solution and/or debris from the surface to
be cleaned is picked up and carried by the air and deposited in the
recovery tank 90 before the air exits the outlet of recovery tank
90. With the path being unobstructed, motor 96 will draw a level of
current from batteries 68, 70, with the level being dependent upon
several factors including but not limited to the voltage of
batteries 68, 70, the type of floor surface being cleaned, and the
specific conditions of squeegee provisions 144. However, if the
path from the inlet of squeegee assembly 152 to the outlet of air
moving device 94 should become blocked, air is unable to flow
through the path and the force required to rotate air moving device
94 decreases. Thus, motor 96 will draw a level of current from
batteries 68, 70 which is less than the level of current when the
air flow path is not blocked.
According to the teachings of the present invention and as
diagrammatically shown in FIG. 4, device 206 detects the level of
current to motor 96. Control circuit 202 monitors the current
detected by device 206 and turns device 210 off and thereby
shutting off vacuum motor 96 in the event that the level of current
drops to a fixed percentage over a fixed period of time. The fixed
period of time can be determined by timing how long it takes for
the current level to drop to its minimum level once the inlet to
squeegee assembly 152 is intentionally blocked and in the preferred
form is 4 seconds. Likewise, the fixed percentage can be determined
by measuring the current to vacuum motor 96 with a normal,
unblocked air flow path and a blocked air flow path such as by
intentionally blocking the inlet to squeegee assembly 152 and in
the preferred form is 84%.
It should be appreciated that the time delay also does not result
in turning off power to vacuum motor 96 in the event that the inlet
to squeegee assembly 152 becomes momentarily restricted in normal
use. Specifically, as diagrammatically shown in FIG. 5, the level
of current drawn by motor 96 will drop (potentially even to the
fixed percentage level) in the event that the inlet to squeegee
assembly 152 becomes momentarily blocked. However, if the blockage
lasts less than the fixed period of time, the level of current
drawn by motor 96 will increase to normal levels when the blockage
is removed and power will continue to be supplied to motor 96. In
the preferred form, the shut off of vacuum motor 96 is controlled
by monitoring for a relative drop in current rather than a fixed
threshold as in the automatic shut off of brush motor 60 because of
the relatively low levels of current to vacuum motor 96 as compared
to brush motor 60 and the variable level of current to vacuum motor
96 under various operating conditions.
In normal operation, the air flow path would be blocked whenever
the level of the solution in recovery tank 90 is such that
mechanical float 170 will block the outlet of recovery tank 90 and
the inlet to air moving device 94. Thus, the operator will
generally become immediately aware that recovery tank 90 is full
because vacuum motor 96 will stop resulting in a change in the
sound of floor scrubber 10 which should be readily ascertainable
and/or because of a light on the console of floor scrubber 10
providing a visible indication. However, in addition to stopping
vacuum motor 96 in the event that recovery tank 90 is full, the
operation of vacuum motor 96 will be interrupted when a blockage
occurs in the path of the air (other than for a momentary
restriction) including but not limited to when the inlet of
squeegee assembly 152 becomes blocked.
It should be appreciated that although apparatus 200 has been
explained in connection with a wet type vacuum assembly according
to the teachings of the present invention, apparatus 200 can have
application in other types of vacuum assemblies. As an example, the
operation of vacuum motor 96 could be interrupted in the path of
air through the vacuum assembly such as the result of clogging the
filters or filter bags in a particulate vacuum assembly and
similarly would protect air moving device 94 and vacuum motor 96
therein.
In the most preferred form, control circuit 202 can also monitor
motors 60 and 96 for abnormally high levels of current.
specifically, control circuit 202 can be programmed to act like a
circuit breaker in that the time before interrupting devices 208
and 210 are turned off can depend on the severity of the overload
condition. For example, if motor 60 or 96 is only slightly
overloaded, apparatus 200 can allow the overloaded motor 60 or 96
to run for a period of time such as 10 minutes before corresponding
device 208 and 210 is turned off. However in the event of a severe
overload such as in the case of a locked agitator 64 or air moving
device 94, the corresponding motor 60 and 96 would be automatically
shut off almost instantly. Further, control circuit 202 can also
include provisions for shutting off motors 60 and 96 in the event
that the voltage of batteries 68, 70 becomes low or in the event
that floor scrubber 10 tilts beyond a fixed angle from a normal
operating position such as in the event that scrubber 10 is tilted
to obtain access to agitator 64.
Thus since the invention disclosed herein may be embodied in other
specific forms without departing from the spirit or general
characteristics thereof, some of which forms have been indicated,
the embodiments described herein are to be considered in all
respects illustrative and not restrictive. The scope of the
invention is to be indicated by the appended claims, rather than by
the foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are intended to be
embraced therein.
* * * * *